System.AccessViolationException Exception

System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at System.Net.Configuration.WebRequestModulesSectionInternal..ctor(WebRequestModulesSection section) at System.Net.Configuration.WebRequestModulesSectionInternal.GetSection()
at System.Net.WebRequest.get_PrefixList() at System.Net.WebRequest.Create(Uri requestUri, Boolean useUriBase) at System.Net.WebRequest.Create(String requestUriString) at Facebook.API.FacebookAPI.GetQueryResponse(String requestUrl, String postString) at Facebook.API.FacebookAPI.ExecuteApiCallString(IDictionary`2
parameterDictionary, Boolean useSession) at Facebook.API.FacebookAPI.GetUserInfoXml(String userIds) at Facebook.API.FacebookAPI.GetUserInfo(String userIds) at Facebook.API.FacebookAPI.GetUserInfo() at _Default.Page_Load(Object sender, EventArgs e) in